This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Persistent diarrhea is the predominant clinical sign of gastrointestinal (GI) disease and is one of the leading causes of morbidity in captive nonhuman primates (NHPs). It has been estimated that in approximately 50% of cases, the etiology of diarrhea is undetermined. The purpose of this resource-related research project is to examine the role of selected, recently recognized and/or under-diagnosed causes of GI disease in the TNPRC rhesus breeding colonies and to develop intervention strategies that can be applied toward the long-term goal of reducing morbidity in rhesus macaques at the TNPRC. To begin to achieve these goals, the specific aims are;1) determine the prevalence and incidence of selected, recently recognized and/or under-diagnosed infectious causes of GI disease in rhesus macaques at the TNPRC to evaluate their association and risk with GI disease, 2) evaluate the association between dietary gluten sensitivity in relation to GI disease, immune status, and demographic factors, and 3) develop intervention strategies for reducing the incidence of GI disease. During this reporting period, fecal specimens obtained from rhesus macaques admitted to the veterinary clinics for diarrhea and / or wounding were evaluated for microsporidia shedding using PCR diagnostics. Of 70 animals, 21 (29% overall prevalence) were positive for spore shedding. Two of the animals were positive for both Enterocytozoon bieneusi and Encephalitozoon sp., 6 were positive for Encephalitozoon sp. only, and the majority of 17 monkeys were positive for E. bieneusi only. The highest prevalence of clinical specimens was submitted from the 1 to 5 -year-old animals and the highest prevalence of microsporidia-positive animals were from the two youngest groups of animals. Testing of microsporidia shedding will continue on specimens collected from asymptomatic animals during the inventory evaluations to compare demographics of microsporidia shedding from symptomatic and asymptomatic animals among the different age groups. Also during this study period, serodiagnostics for caliciviruses were performed on 132 rhesus macaques in the breeding colony. Positive ELISA reactivity was observed in 88 (66%) and 72(54%) of sera against norovirus Norwalk and MOH strains, respectively and 58 (44%) and 78 (59%) of sera were positive for antibodies against sapovirus Mex14917 and Mex340 strains, respectively. Furthermore, 1 [unreadable]2 % of rhesus macaques exhibited seroconversion to gliadin, indicative of gluten sensitivity.